This invention relates to a document filing system for sequentially storing picture information on, for example, a document in a memory device and for retrieving and reading out the stored picture information stored. More specifically, this invention relates to a document size conversion circuit to be used in such a document filing system.
A document filing system, which has recently been developed, is adapted to scan picture information on a document by optical two-dimensional scanning using a laser for example. The scanned picture information is stored in a memory device in such a manner that it can be retrieved from among other various picture information stored in the memory device and read. Then it may be visually displayed on the screen of a CRT display device or printed paper using a printing device.
In the document filing system, the scanned picture information is first stored in a page buffer constituting a buffer memory and after one unit (one page) of picture information has been accumulated in the page buffer, it is stored in a memory device. Upon outputting the picture information stored in the memory device, the information is stored in the page buffer and then is supplied to the CRT display device or to the printing device. A variety of picture information is stored in the document filing system and a variety of paper sizes including B5 and B4 is used for the contents of the picture information. For a greater document size a page buffer of a corresponding capacity is necessary. However, a greater-capacity page buffer involves an increase in cost and requires more space. In order to display the picture information in the original state, a large CRT display device is required.
In order to cope with such problems it has been contemplated to divide such larger-sized picture information into smaller segments, without increasing the size of the page buffer and CRT display device, and to sequentially process the segments. This method requires much time in retrieving necessary information and outputting it. For this reason, demand has grown for a document filing system adapted to store one unit (one page) of picture information for display at the same time, without increasing the size of the buffer memory capacity and CRT display device, which can perform information retrieval very efficiently.